SANTA CLARA, Calif. — Who’s got it better than the San Francisco 49ers? Nobody, at least when it comes to inside linebackers.

Patrick Willis and NaVorro Bowman have been the driving forces behind a couple of key numbers that display the stingy success of the 49ers’ defense. San Francisco is holding opponents to a league-low average of 77.2 yards rushing per game and only 14.3 points per game—one-tenth of one point behind the Pittsburgh Steelers’ league-best figure.

Willis and Bowman combined for 18 solo tackles, 19 overall, in a 36-32 victory over the New Orleans Saints in an NFC divisional playoff game last Saturday. Time and again, Willis and Bowman met Saints running back Darren Sproles a split second after Sproles hauled in one of his 15 catches. Sproles netted only 75 yards on 14 of those, with 44 more coming on one reception against zone coverage.

“A huge part of their success is their ability to stop the run and rush the passer,” Saints quarterback Drew Brees said. “And when you catch the ball, they are going to light you up and try to get the ball out.”

Outside linebackers Ahmad Brooks and Aldon Smith round out a linebacking unit that forms the heart of the 49ers’ defense and soon might be regarded as the league’s best. And considering Brooks, 27, is the oldest member of the unit, it could be the league’s best for a while. Willis said the unit’s approach stems from a mind-set instilled in them by first-year coach Jim Harbaugh.

“Every time we step on that field, it’s about not giving the other teams anything,” Willis said. “It’s something that coach Harbaugh talks about all of the time: cruelty.

“It’s not giving another person what they want. That’s our mind-set on defense, to go out and play with everything we have and not give the other team anything. If they do get something, oh, well, let’s go and take it back.”

Time and again, that’s what the 49ers did this season, as they finished with a league-best plus-28 takeaway-giveaway differential. Overall, the 49ers intercepted 23 passes and forced 31 fumbles, with 15 recovered.

Against the Saints, the 49ers forced five turnovers. Willis recovered one fumble, at the 49ers’ 2-yard line as the Saints threatened on a game-opening drive. That Willis is recognized as the engine that makes the rest of the defense go comes as no surprise to those who witnessed his upbringing in Bruceton, Tenn., in the midst of poverty, constant hardships and a childhood cut short by forced maturation.

Willis’ mother left home when he was 4, ultimately leaving Willis to work an array of odd jobs, including picking cotton from the time he was 10 years old, and basically to raise his three younger siblings.

He found refuge as a three-sport star in high school, which resulted in a full-ride scholarship to Ole Miss. He played with Ravens offensive tackle Michael Oher, the subject of the acclaimed book and movie, “The Blindside.”

There are those who say Willis’ upbringing would make for an even more-compelling movie than the one based on Oher’s path from a hardscrabble life to the NFL.

Willis isn’t without flaws, as evidenced by Saints tight end Jimmy Graham beating him for two touchdowns last Saturday.

It’s those rare occasions when Willis isn’t dominant that fuel his ever-burning desire to work harder, study more tape and find ways to keep getting better.

“I was hurting,” Willis said of his inability to shut down Graham, who succeeded against just about everybody else this season. “I was down because I know that my teammates always count on me to be the defensive player that I am. … To have a chance of redeeming myself feels great.”

Willis’ play this season was expected. He now has earned Pro Bowl appearances in all five of his seasons and has been first-team All-Pro four times. He is regarded as, perhaps, the game’s best all-around linebacker.

In Bowman, the 49ers had only a hunch that he had what it takes to blossom into an elite player, even though Bowman didn’t give much of an indication of his ability during rookie season in 2010.

The 49ers were so confident in Bowman—a third-round pick—that they parted ways with well-respected veteran Takeo Spikes after last season and handed the job to Bowman.

Bowman felt the pressure and realized that all eyes were upon him from the outset.

“Takeo’s been in the league for a long time and for them to release him for a young guy that doesn’t have any film in this league, that would make them nervous,” Bowman said. “So I definitely came in with a chip on my shoulder.

“I wanted to definitely prove myself. Week in, week out, I never got complacent, whether I had a good game or an all- right game. I just wanted to keep getting better and prepare the best I can against those opponents and have a good game.”

It would be folly to think Bowman would play as well as Spikes, let alone at an elite level. Yet, he played so well all season that many feel as if he had a better season than Willis.

“He’s our leading tackler,” Harbaugh said of Bowman. “To do that alongside of Patrick Willis, they have done a phenomenal job of playing great football, playing together well, playing within the framework of the defense really well. And already in his second year he’s doing a tremendous job.”

Bowman posted 143 tackles, including two sacks, and he broke up seven passes. As a rookie, he had 46 tackles, no sacks and no passes defensed.

Smith’s ascension into a dominant pass rusher in only his rookie season is well chronicled by now. The 49ers surprised some by taking Smith with the seventh pick in the 2011 NFL draft.

There was concern just how effective Smith would be this season, given he was converting from defensive end at Missouri to outside linebacker in the NFL and doing so without benefit of offseason workouts.

Smith answered those questions right away, using his rare combination of speed, strength and determination to develop into one of the league’s top pass-rushers. He finished with 14 sacks this season, one-half sack shy of tying Javon Kearse’s NFL rookie record.

With six years of experience (including four in San Francisco), Brooks qualifies as the senior member of the unit. In keeping with San Francisco's superb linebacker play this season, he recorded career highs in tackles (50) and sacks (seven). Brooks is scheduled to become a free agent after the season, but look for him to re-sign.

San Francisco’s linebacking corps is so dominant most games that Willis feels as if he and his three linebacking mates are able to dictate the outcome of a game.

“Regardless if we’re playing the Saints or whoever else, we have to come out and play football,” Willis said. “At the end of the day, I always put it on us. It’s not so much about how the other team plays, it’s about how we play.”